refactoing containers out of the main module.

* bump version to `1.2.0`
* adding `assert.hpp` module
* adding testing example to check the `assert.hpp` module
* updating examples in the RAEDME file
* updating LICENSE file and in all code modules.

adding heterogeneous container.

updating workflow to package.

adding version defines back, bump minor.

refactoring project file tree examples into code units.

updating readme, executable name, and header order.

project init.